This invention concerns the continuous chromium-plating of bars, long pieces of variable sizes and cross-sections, and the like, which foresees the use of a particular system for removing the hydrogen formed during the chromium-plating process which would otherwise tend to adhere to the surfaces of the pieces, in the portion of the path delimited by the chromium-plating electrode allowing an even deposit of the chromium itself.
This invention concerns, moreover, a double-tank apparatus, in particular for hard, or thick, chromium-plating of bars, meaning by this, large elongated pieces having either a continuous or variable profile, such apparatus being provided with a double sealing device for recovering the chromium-plating fluid, and with a system for recycling the chromium-plating fluid, in order to eliminate deposits of hydrogen on the surfaces of the bars, in the portion of the path delimited by the chromium-plating anode. There are known apparatuses for continuously chromium-plating bars and the like, which foresee the use of a system of tanks through which the bar or series of bars, to be chromium-plated, travel; however, the known types of apparatuses are very rarely suitable for hard or thick chromium-plating of large-sized pieces due to the problem of the hydrogen which is generated in the chromium-plating bath. This is a serious draw-back because this hydrogen tends to adhere to the surfaces of the piece to be chromium-plated, in the portion of the path defined by the chromium-plating anode, preventing an even deposit of chrome. This problem is particularly serious with bars or pieces of large dimensions having a variable or non-circular cross-sectional profile, because of the tendency of the hydrogen to adhere to the downward facing surfaces of the bar, due to the impossibility of rotating bars or pieces of a considerable length and which may be as wide as 30-40 cm or more.
With apparatuses of the aforementioned type, there is also the problem of ensuring a perfect seal at the bar entrance and exit ends of the chromium-plating tanks, insofar as this seal is difficult to achieve due to the very nature and properties of the chromium-plating bath, together with the fact that in pieces or bars with particular cross-sectional shapes, the profile may vary abruptly along the axis of the bar or of the piece itself. It is obvious that in such conditions the chromium-plating fluid could suddenly overflow from the tank, with a consequent serious danger for the objects and personnel in charge of the chromium-plating plant.
These problems have never been tackled and solved in practice or in such a way as to ensure the proper functioning of the apparatus in order to achieve a perfect chromium-plating of bars or pieces in general, providing a constant and even layer of chrome over the entire surface of the piece itself.
A scope of this invention is to provide a method for eliminating the hydrogen in a chromium-plating bath for bars and pieces of large dimensions, which makes it possible to obtain a layer of chrome of homogenous thickness on pieces to be chromium-plated, by eliminating the serious problem caused by the adhesion of hydrogen to the piece itself.
A further scope of this invention is to provide an apparatus by means of which it is possible to carry out the above-described method, which apparatus is provided with a recycling system and a double tank with sealing means on the sides, in order to prevent any overflow of fluid whatsoever, and at the same time fitting itself to pieces or bars of variable cross-sectional shapes and sizes.